Air mattresses are used with cots and beds to provide yieldable body supports. The air mattresses are inflated with pumps, such as hand operated pumps and bag pumps. Motor driven blowers and pumps have also been used to supply air under pressure to air mattresses. The biasing or firmness characteristic of an air mattress is determined by the pressure of the air in the air mattress. The air mattress firmness can be varied by supplying additional air or venting air from the air mattress. Control mechanisms have been used to adjust the inflation of air mattresses. Young et al in U.S. Pat. No. 4,244,706 discloses a mechanism for adjusting the amount of air in an air mattress. The mechanism includes bladders connected to air mattresses for supplying air to and receiving air from the air mattresses. The internal volumes of the bladders are changed to adjust the pressure of the air in the air mattresses. Other control mechanisms operable to adjust the inflation of air mattresses are disclosed in U.S. Pat. Nos. 3,605,138; 3,784,944; 3,822,425; and 4,394,784.